idnits 2.17.1 draft-xie-idr-bgpls-sr-vtn-mt-02.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (January 26, 2021) is 1157 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC5029' is defined on line 352, but no explicit reference was found in the text == Unused Reference: 'I-D.dong-lsr-sr-enhanced-vpn' is defined on line 375, but no explicit reference was found in the text == Unused Reference: 'I-D.ietf-lsr-isis-srv6-extensions' is defined on line 381, but no explicit reference was found in the text == Unused Reference: 'RFC8667' is defined on line 405, but no explicit reference was found in the text ** Downref: Normative reference to an Informational draft: draft-dong-spring-sr-for-enhanced-vpn (ref. 'I-D.dong-spring-sr-for-enhanced-vpn') == Outdated reference: A later version (-18) exists of draft-ietf-idr-bgp-ls-segment-routing-ext-16 == Outdated reference: A later version (-14) exists of draft-ietf-idr-bgpls-srv6-ext-05 == Outdated reference: A later version (-17) exists of draft-ietf-idr-rfc7752bis-05 == Outdated reference: A later version (-08) exists of draft-ietf-spring-resource-aware-segments-01 ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) == Outdated reference: A later version (-05) exists of draft-dong-idr-bgpls-sr-enhanced-vpn-02 == Outdated reference: A later version (-10) exists of draft-dong-lsr-sr-enhanced-vpn-04 == Outdated reference: A later version (-19) exists of draft-ietf-lsr-isis-srv6-extensions-11 == Outdated reference: A later version (-17) exists of draft-ietf-teas-enhanced-vpn-06 == Outdated reference: A later version (-03) exists of draft-xie-lsr-isis-sr-vtn-mt-02 Summary: 2 errors (**), 0 flaws (~~), 14 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group C. Xie 3 Internet-Draft C. Li 4 Intended status: Standards Track China Telecom 5 Expires: July 30, 2021 J. Dong 6 Z. Li 7 Huawei Technologies 8 January 26, 2021 10 BGP-LS with Multi-topology for Segment Routing based Virtual Transport 11 Networks 12 draft-xie-idr-bgpls-sr-vtn-mt-02 14 Abstract 16 Enhanced VPN (VPN+) aims to provide enhanced VPN service to support 17 some applications' needs of enhanced isolation and stringent 18 performance requirements. VPN+ requires integration between the 19 overlay VPN and the underlay network. A Virtual Transport Network 20 (VTN) is a virtual underlay network which consists of a customized 21 network topology and a set of network resource allocated from the 22 physical network. A VTN could be used as the underlay to support one 23 or a group of VPN+ services. 25 When Segment Routing is used as the data plane of VTNs, each VTN can 26 be allocated with a group of SIDs to identify the topology and 27 resource attributes of network segments in the VTN. The association 28 between the network topology, the network resource attributes and the 29 SR SIDs may need to be distributed to a centralized network 30 controller. For network scenarios where each VTN can be identified 31 by a unique topology ID, this document describes a mechanism to 32 distribute the information of SR based VTNs using BGP-LS with Multi- 33 Topology. 35 Requirements Language 37 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 38 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 39 document are to be interpreted as described in RFC 2119 [RFC2119]. 41 Status of This Memo 43 This Internet-Draft is submitted in full conformance with the 44 provisions of BCP 78 and BCP 79. 46 Internet-Drafts are working documents of the Internet Engineering 47 Task Force (IETF). Note that other groups may also distribute 48 working documents as Internet-Drafts. The list of current Internet- 49 Drafts is at https://datatracker.ietf.org/drafts/current/. 51 Internet-Drafts are draft documents valid for a maximum of six months 52 and may be updated, replaced, or obsoleted by other documents at any 53 time. It is inappropriate to use Internet-Drafts as reference 54 material or to cite them other than as "work in progress." 56 This Internet-Draft will expire on July 30, 2021. 58 Copyright Notice 60 Copyright (c) 2021 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (https://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 76 2. Advertisement of SR VTN Topology Attribute . . . . . . . . . 3 77 2.1. Intra-domain Topology Advertisement . . . . . . . . . . . 4 78 2.2. Inter-Domain Topology Advertisement . . . . . . . . . . . 5 79 3. Advertisement of SR VTN Resource Attribute . . . . . . . . . 6 80 4. Scalability Considerations . . . . . . . . . . . . . . . . . 6 81 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 82 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 83 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 84 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 85 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 86 8.2. Informative References . . . . . . . . . . . . . . . . . 8 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 89 1. Introduction 91 Enhanced VPN (VPN+) is an enhancement to VPN services to support the 92 needs of new applications, particularly including the applications 93 that are associated with 5G services. These applications require 94 enhanced isolation and have more stringent performance requirements 95 than that can be provided with traditional overlay VPNs. Thus these 96 properties require integration between the overlay connectivity and 97 the characteristics provided by the underlay networks. 98 [I-D.ietf-teas-enhanced-vpn] specifies the framework of enhanced VPN 99 and describes the candidate component technologies in different 100 network planes and layers. An enhanced VPN can be used for 5G 101 network slicing, and will also be of use in more generic scenarios. 103 To meet the requirement of enhanced VPN services, a number of Virtual 104 Transport Networks (VTNs) need to be created, each consists of a 105 subset of the underlay network topology and a set of network 106 resources allocated from the underlay network to meet the requirement 107 of one or a group of VPN+ services. 109 [I-D.ietf-spring-resource-aware-segments] introduces resource 110 awareness to Segment Routing (SR) [RFC8402], by associating existing 111 type of SIDs with network resource attributes (e.g. bandwidth, 112 processing or storage resources). These resource-aware SIDs retain 113 their original functionality, with the additional semantics of 114 identifying the set of network resources available for the packet 115 processing action.[I-D.dong-spring-sr-for-enhanced-vpn] describes the 116 use of resource-aware segments to build SR based VTNs. To allow the 117 network controller and network nodes to perform VTN-specific explicit 118 path computation and/or shortest path computation, the group of 119 resource-aware SIDs allocated by network nodes to each VTN and the 120 associated topology and resource attributes need to be distributed in 121 the control plane. When a centralized network controller is used for 122 VTN-specific path computation, especially when a VTN spans multiple 123 IGP areas or multiple Autonomous Systems (ASes), BGP-LS is needed to 124 advertise the VTN information in each IGP area or AS to the network 125 controller, so that the controller could use the collected 126 information to build the view of inter-area or inter-AS SR VTNs. 128 In some network scenarios, each VTN can be identified by a unique 129 topology ID [RFC5120], [I-D.xie-lsr-isis-sr-vtn-mt] describes an IGP 130 mechanism to advertise the association between the topology, resource 131 attributes and the SR SIDs for each VTN. This document describes a 132 mechanism to distribute the information of SR based VTNs to the 133 network controller using BGP-LS with Multi-Topology. 135 2. Advertisement of SR VTN Topology Attribute 137 [I-D.xie-lsr-isis-sr-vtn-mt] describes the IS-IS Multi-topology based 138 mechanisms to distribute the topology attributes of SR based VTNs. 139 This section describes the corresponding BGP-LS mechanism to 140 distribute both the intra-domain and inter-domain topology attributes 141 of SR based VTNs. 143 2.1. Intra-domain Topology Advertisement 145 In section 4.2.2.1 of [I-D.ietf-idr-rfc7752bis], Multi-Topology 146 Identifier (MT-ID) TLV is defined, which can contain one or more IS- 147 IS or OSPF Multi-Topology IDs. The MT-ID TLV MAY be present in a 148 Link Descriptor, a Prefix Descriptor, or the BGP-LS Attribute of a 149 Node NLRI. 151 [I-D.ietf-idr-bgp-ls-segment-routing-ext] defines the BGP-LS 152 extensions to carry the segment routing information using TLVs of 153 BGP-LS Attribute. When MTR is used with SR-MPLS data plane, 154 topology-specific prefix-SIDs and topology-specific Adj-SIDs can be 155 carried in the BGP-LS Attribute associated with the prefix NLRI and 156 link NLRI respectively, the MT-ID TLV is carried in the prefix 157 descriptor or link descriptor to identify the corresponding topology 158 of the SIDs. 160 [I-D.ietf-idr-bgpls-srv6-ext] defines the BGP-LS extensions to 161 advertise SRv6 segments along with their functions and attributes. 162 When MTR is used with SRv6 data plane, the SRv6 Locator TLV is 163 carried in the BGP-LS Attribute associated with the prefix-NLRI, the 164 MT-ID TLV can be carried in the prefix descriptor to identify the 165 corresponding topology of the SRv6 Locator. The SRv6 End.X SIDs are 166 carried in the BGP-LS Attribute associated with the link NLRI, the 167 MT-ID TLV can be carried in the link descriptor to identify the 168 corresponding topology of the End.X SIDs. The SRv6 SID NLRI is 169 defined to advertise other types of SRv6 SIDs, in which the SRv6 SID 170 Descriptors can include the MT-ID TLV so as to advertise topology- 171 specific SRv6 SIDs. 173 [I-D.ietf-idr-rfc7752bis] also defines the rules of the usage of MT- 174 ID TLV: 176 "In a Link or Prefix Descriptor, only a single MT-ID TLV containing 177 the MT-ID of the topology where the link or the prefix is reachable 178 is allowed. In case one wants to advertise multiple topologies for a 179 given Link Descriptor or Prefix Descriptor, multiple NLRIs MUST be 180 generated where each NLRI contains a single unique MT-ID." 182 Editor's note: the above rules indicates that only one MT-ID is 183 allowed to be carried the Link or Prefix descriptors. When a link or 184 prefix needs to be advertised in multiple topologies, multiple NLRIs 185 needs to be generated to report all the topologies the link or prefix 186 participates in, together with the topology-specific segment routing 187 information and link attributes. This may increase the number of BGP 188 Updates needed for advertising MT-specific topology attributes, and 189 may introduce additional processing burden to both the sending BGP 190 speaker and the receiving network controller. When the number of 191 topologies in a network is not a small number, some optimization may 192 be needed for the reporting of multi-topology information and the 193 associated segment routing information in BGP-LS. Based on the WG's 194 opinion, this will be elaborated in a future version. 196 2.2. Inter-Domain Topology Advertisement 198 [I-D.ietf-idr-bgpls-segment-routing-epe] and 199 [I-D.ietf-idr-bgpls-srv6-ext] defines the BGP-LS extensions for 200 advertisement of BGP topology information between ASes and the BGP 201 Peering Segment Identifiers. Such information could be used by a 202 network controller for the computation and instantiation of inter-AS 203 traffic engineering SR paths. 205 In some network scenarios, there are needs to create VTNs which span 206 multiple ASes. The inter-domain VTNs could have different inter- 207 domain connectivity, and may be associated with different set of 208 network resources in each domain and also on the inter-domain links. 209 In order to build the multi-domain SR based VTNs, it is necessary to 210 advertise the topology and resource attribute of each VTN and the 211 associated BGP Peering SIDs on the inter-domain links. 213 Depending on the requirement of inter-domain VTNs, different 214 mechanism can be used on the inter-domain connection: 216 o One EBGP session between two ASes can be established over multiple 217 underlying links. In this case, different underlying links can be 218 used for different inter-domain VTNs which requires link isolation 219 between each other. In another similar case, the EBGP session is 220 established over a single link, while the network resource (e.g. 221 bandwidth) on this link can be partitioned into several pieces, 222 each of which can be considered as a virtual member link. A VTN 223 is associated with one of the physical or virtual member links. 224 In both cases, different BGP Peer-Adj-SIDs or SRv6 End.X SID 225 SHOULD be allocated to each underlying physical or virtual member 226 link, the association between the BGP Peer Adj-SID/End.X SID and 227 the identifier of the VTN SHOULD be advertised by the ASBR. 229 o For inter-domain connection between two ASes, multiple EBGP 230 sessions can be established between different set of peering 231 ASBRs. It is possible that some of these BGP sessions are used 232 for one multi-domain VTN, while some other BGP sessions are used 233 for another multi-domain VTN. In this case, different BGP Peer 234 Node SIDs are allocated to each BGP session and are advertised 235 using the mechanism in [I-D.ietf-idr-bgpls-segment-routing-epe] 236 and [I-D.ietf-idr-bgpls-srv6-ext], the association between the BGP 237 Peer Node SIDs and the identifier of the VTN SHOULD be advertised 238 by the ASBR. 240 o At the AS-level topology, different multi-domain VTNs may have 241 different inter-domain connectivity. Different BGP Peer Set SIDs 242 MAY be allocated to represent the groups of BGP peers which can be 243 used for load-balancing in each multi-domain VTN. 245 When MT-ID is used consistently in multiple ASes covered by a VTN, 246 the topology-specific BGP peering SIDs can be advertised with the MT- 247 ID carried in the corresponding Link NLRI. This can be achieved with 248 the existing mechanisms as defined in 249 [RFC7752][I-D.ietf-idr-bgpls-segment-routing-epe] and 250 [I-D.ietf-idr-bgpls-srv6-ext]. 252 In network scenarios where consistent usage of MT-ID among multiple 253 domains can not be expected, a global-significant VTN-ID needs to be 254 introduced to define the inter-domain topologies. Within each 255 domain, the MT based mechanism could be reused for intra-domain 256 topology advertisement. The detailed mechanism is specified in 257 [I-D.dong-idr-bgpls-sr-enhanced-vpn]. 259 3. Advertisement of SR VTN Resource Attribute 261 [I-D.xie-lsr-isis-sr-vtn-mt] specifies the mechanism to advertise the 262 resource information associated with each VTN. This section 263 describes the corresponding BGP-LS mechanisms. 265 The information of the network resources associated with a VTN can be 266 specified by carrying the TE Link attribute TLVs in BGP-LS Attribute 267 [RFC7752], with the associated MT-ID carried in the corresponding 268 Link NLRI. 270 When Maximum Link Bandwidth sub-TLV is carried in the BGP-LS 271 attribute associated with the Link NLRI of a VTN, it indicates the 272 amount of link bandwidth resource allocated to the corresponding VTN 273 on the link. The bandwidth allocated to a VTN can be exclusive for 274 traffic in the corresponding VTN. The advertisement of other TE 275 attributes in BGP-LS for each VTN is for further study. 277 4. Scalability Considerations 279 The mechanism described in this document requires that each VTN 280 mapped to an independent topology, and for the inter-domain VTNs, the 281 MT-IDs used in each involved domain need to be consistent. Reusing 282 MT-IDs as the identifier of VTN can avoid introducing new identifiers 283 in the control plane, while it also has some limitations. For 284 example, when multiple VTNs shares the same topology, each VTN still 285 need to be identified using different MT-IDs in the control plane, 286 thus independent path computation needs be executed for each VTN. 287 The number of VTNs supported in a network may be dependent on the 288 number of topologies supported, which is related to the control plane 289 overhead. 291 5. Security Considerations 293 This document introduces no additional security vulnerabilities to 294 BGP-LS. 296 The mechanism proposed in this document is subject to the same 297 vulnerabilities as any other protocol that relies on BGP-LS. 299 6. IANA Considerations 301 This document does not request any IANA actions. 303 7. Acknowledgments 305 The authors would like to thank Shunwan Zhuang for the review and 306 discussion of this document. 308 8. References 310 8.1. Normative References 312 [I-D.dong-spring-sr-for-enhanced-vpn] 313 Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, 314 Z., and F. Clad, "Segment Routing based Virtual Transport 315 Network (VTN) for Enhanced VPN", draft-dong-spring-sr-for- 316 enhanced-vpn-13 (work in progress), January 2021. 318 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 319 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 320 and M. Chen, "BGP Link-State extensions for Segment 321 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 322 (work in progress), June 2019. 324 [I-D.ietf-idr-bgpls-segment-routing-epe] 325 Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray, 326 S., and J. Dong, "BGP-LS extensions for Segment Routing 327 BGP Egress Peer Engineering", draft-ietf-idr-bgpls- 328 segment-routing-epe-19 (work in progress), May 2019. 330 [I-D.ietf-idr-bgpls-srv6-ext] 331 Dawra, G., Filsfils, C., Talaulikar, K., Chen, M., 332 daniel.bernier@bell.ca, d., and B. Decraene, "BGP Link 333 State Extensions for SRv6", draft-ietf-idr-bgpls- 334 srv6-ext-05 (work in progress), November 2020. 336 [I-D.ietf-idr-rfc7752bis] 337 Talaulikar, K., "Distribution of Link-State and Traffic 338 Engineering Information Using BGP", draft-ietf-idr- 339 rfc7752bis-05 (work in progress), November 2020. 341 [I-D.ietf-spring-resource-aware-segments] 342 Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, 343 Z., and F. Clad, "Introducing Resource Awareness to SR 344 Segments", draft-ietf-spring-resource-aware-segments-01 345 (work in progress), January 2021. 347 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 348 Requirement Levels", BCP 14, RFC 2119, 349 DOI 10.17487/RFC2119, March 1997, 350 . 352 [RFC5029] Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link 353 Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029, 354 September 2007, . 356 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 357 S. Ray, "North-Bound Distribution of Link-State and 358 Traffic Engineering (TE) Information Using BGP", RFC 7752, 359 DOI 10.17487/RFC7752, March 2016, 360 . 362 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 363 Decraene, B., Litkowski, S., and R. Shakir, "Segment 364 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 365 July 2018, . 367 8.2. Informative References 369 [I-D.dong-idr-bgpls-sr-enhanced-vpn] 370 Dong, J., Hu, Z., Li, Z., Tang, X., and R. Pang, "BGP-LS 371 Extensions for Segment Routing based Enhanced VPN", draft- 372 dong-idr-bgpls-sr-enhanced-vpn-02 (work in progress), June 373 2020. 375 [I-D.dong-lsr-sr-enhanced-vpn] 376 Dong, J., Hu, Z., Li, Z., Tang, X., Pang, R., JooHeon, L., 377 and S. Bryant, "IGP Extensions for Segment Routing based 378 Enhanced VPN", draft-dong-lsr-sr-enhanced-vpn-04 (work in 379 progress), June 2020. 381 [I-D.ietf-lsr-isis-srv6-extensions] 382 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 383 Z. Hu, "IS-IS Extension to Support Segment Routing over 384 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-11 385 (work in progress), October 2020. 387 [I-D.ietf-teas-enhanced-vpn] 388 Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A 389 Framework for Enhanced Virtual Private Networks (VPN+) 390 Service", draft-ietf-teas-enhanced-vpn-06 (work in 391 progress), July 2020. 393 [I-D.xie-lsr-isis-sr-vtn-mt] 394 Xie, C., Ma, C., Dong, J., and Z. Li, "Using IS-IS Multi- 395 Topology (MT) for Segment Routing based Virtual Transport 396 Network", draft-xie-lsr-isis-sr-vtn-mt-02 (work in 397 progress), October 2020. 399 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 400 Topology (MT) Routing in Intermediate System to 401 Intermediate Systems (IS-ISs)", RFC 5120, 402 DOI 10.17487/RFC5120, February 2008, 403 . 405 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 406 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 407 Extensions for Segment Routing", RFC 8667, 408 DOI 10.17487/RFC8667, December 2019, 409 . 411 Authors' Addresses 413 Chongfeng Xie 414 China Telecom 415 China Telecom Beijing Information Science & Technology, Beiqijia 416 Beijing 102209 417 China 419 Email: xiechf@chinatelecom.cn 421 Cong Li 422 China Telecom 423 China Telecom Beijing Information Science & Technology, Beiqijia 424 Beijing 102209 425 China 427 Email: licong@chinatelecom.cn 428 Jie Dong 429 Huawei Technologies 430 Huawei Campus, No. 156 Beiqing Road 431 Beijing 100095 432 China 434 Email: jie.dong@huawei.com 436 Zhenbin Li 437 Huawei Technologies 438 Huawei Campus, No. 156 Beiqing Road 439 Beijing 100095 440 China 442 Email: lizhenbin@huawei.com